n 2006 the number of Americans who were members of a health club was 42.7 million. This was an increase of 106% from the number of clubs in 1990. How many Americans were health club members in 1990? 

Step 1. 106% means 1.06 in decimal form. 

Step 2. Let x be the number of Americans who were health club numbers in 1990 

Step 3. Let 1.06x be the amount of increase from 1990. 

Step 4. Then x+1.06x=42.7 million be the current amount of 42.7. 

Step 5. Solving x+1.06x=42.7 yields the following steps 

2.06x=42.7

Divide by 2.06 to both sides of the equation 

Step 6. ANSWER: The number of club members in 1990 is 20.73 million.